1. Field of the Invention
The present invention relates to a tobacco product produced by wrapping cut tobacco with a pouch or a cigarette paper.
2. Description of the Related Art
SNUS may be spotted on the pouch after it is produced and before it is delivered to a user. Occurrence of spots on the pouch of SNUS causes a problem such that a user has an impression of reduced quality of the product. Accordingly, it is desired to suppress spots as much as possible. There is the same problem of spots on cigarette paper. The spots occur where a component of cut tobacco, wrapped with a pouch or a cigarette paper, permeates the pouch or the cigarette paper.
Japanese Patent No. 2,660,876 and U.S. Pat. No. 5,143,099 disclose use of double cigarette papers, in which a cigarette paper provided with pores and having a low basis weight and a high air-permeability is used as an inside cigarette paper in order to reduce spots on the cigarette. The documents also disclose applying a sizing agent such as alkali ketene dimer to the paper in order to control surface wettability.
Permeation of a spotting component into the pouch or the cigarette paper is a phenomenon caused by capillary force. The capillary force is reduced as the pore size of the paper is larger, and a permeation distance becomes longer as the pore size of the paper is smaller. In the case where the pore size of the inside cigarette paper is larger than that of the outside cigarette paper as in Japanese Patent No. 2,660,876 and U.S. Pat. No. 5,143,099, when the spotting component penetrates the inside cigarette paper, the spotting component also penetrates the outside cigarette paper. Therefore, the techniques of Japanese Patent No. 2,660,876 and U.S. Pat. No. 5,143,099 intend to reduce spots by simply providing the inside cigarette paper rather than by the effect of the double cigarette papers.
Japanese Patent No. 4,024,249 relates to a smoking product the side stream smoke of which is flavored and discloses that an encapsulated flavor is retained between the inner and outer layers of double cigarette papers, in which the outside cigarette paper has an air permeability of 200 CU or more and the inside cigarette paper has an air permeability lower than that. In Japanese Patent No. 4,024,249, the flavor component is evaporated from the encapsulated flavor provided between the layers of double cigarette papers to facilitate diffusion through the cigarette paper.
However, since Japanese Patent No. 4,024,249 does not take permeation of liquid and spotting into consideration, influence of the air permeability of each of the inside cigarette paper and the outside cigarette paper as well as double cigarette papers on permeation of liquid and spotting are unclear.